CN111971325B

CN111971325B - Laminating adhesive using polyesters from transesterification of polylactic acid with natural oils

Info

Publication number: CN111971325B
Application number: CN201980023474.9A
Authority: CN
Inventors: G·B·肯尼翁; A·P·姆加亚; 昌正缅; B·拉玛林加姆
Original assignee: Henkel AG and Co KGaA
Current assignee: Henkel AG and Co KGaA
Priority date: 2018-04-06
Filing date: 2019-03-28
Publication date: 2023-08-22
Anticipated expiration: 2039-03-28
Also published as: WO2019195066A1; JP7391870B2; CN111971325A; EP3774988A1; EP3774988A4; JP2021521283A

Abstract

The present invention relates to specific mixtures of polyols, wherein at least one of said polyols contains the transesterification product of a polymeric polylactic acid with a natural oil. The mixture of polyols may be used as one component in a two-component adhesive for laminated flexible packaging. The other component comprises an isocyanate-functional compound. The two components are mixed prior to use and the resulting adhesive can be used to bond films to form flexible packaging materials.

Description

Laminating adhesive using polyesters from transesterification of polylactic acid with natural oils

Technical field:

disclosed are two-component laminating adhesives wherein the first component comprises an isocyanate-functional compound, such as an NCO-terminated polyurethane prepolymer; the second component comprises an isocyanate-reactive mixture of polyols, wherein at least one of the polyols comprises the transesterification product of a polymeric polylactic acid with a natural oil. The two components are mixed and the resulting adhesive is useful in forming flexible packaging materials.

The background technology is as follows:

product packaging has been converted from sealed metal cans and glass bottles to sealed flexible packages, such as pouches (pouch). As an example, tuna is available today in both traditional metal cans and soft bags. The shape of the flexible package can be easily changed by user manipulation when filled and closed or sealed with a food or other product. The flexible package is typically made from two layers of flexible packaging material that overlap and are sealed around most of their outer periphery to form a cavity inside. Typically, two layers of flexible packaging material are heat sealed by the application of heat and pressure to fuse the layers together near the thin portions of the package periphery. A food or other product is placed in the cavity through the opening and the opening is closed by heat sealing the open layers together. The sealed package and the closed product may be heated for preservative purposes. In some demanding applications, the sealed package and the closed product may be retorted under pressure, that is, heated to a temperature of 100 ℃ or more.

The flexible packaging material is prepared by laminating two or more films. Each film is selected to obtain specific properties. For example, the flexible packaging material may be a three-layer laminate. The inner layer will contact the packaged product. Polypropylene has desirable product contact properties as well as heat sealability and can be used as an inner layer. The optional intermediate layer may be used to provide a barrier to moisture, oxygen and/or light. The metal film or foil has the desired barrier properties and a metal film such as aluminum foil may be used as an intermediate layer. The outer layer will provide protection for the package and also provide a surface for printing information (e.g., contents, package date, warnings, etc.). The polyester film is tough and receptive to printing inks and can be used as an outer layer. The thickness of the flexible packaging material may be about 13 to about 75 micrometers (0.0005 to 0.003 inches).

Each layer of flexible packaging material is bonded to an adjacent layer by an adhesive. The adhesive may be applied to the layer from a solution in a suitable solvent using gravure or smooth roll coating cylinders, or from a solvent-free state using special application machines, and the layer is laminated to an adjacent layer. The laminated packaging material is dried and piled up as necessary into rolls.

While there are many possible types of adhesives, polyurethane-based adhesives are preferred for use in flexible packaging materials because they possess many desirable properties, including good adhesion to materials in the layers, high peel strength, heat resistance (e.g., heat from heat sealing or pressure cooking), and food resistance. Typically, two-component polyurethane adhesives are used. The first component is an isocyanate-moiety containing (isocyanate-functional) polyurethane prepolymer obtained by the reaction of an excess of diisocyanate with a polyether and/or polyester containing two or more active hydrogen groups per molecule. The second component is typically a polyol. The two components are mixed just prior to use to initiate a curing reaction between the components and applied to the film surface to be laminated.

Solvents are used as diluents for some polyurethane laminating adhesives because the viscosity of those mixed adhesives is too high to reliably apply them in liquid form in a roll-to-roll (roll-to-roll) lamination process. Solvent-based or water-based laminating adhesives are limited by the rate of application at which solvent or water can be effectively removed in an oven. Typical line speeds for solvent-based and water-based laminating adhesives are 300-600 feet/min due to drying limitations. Solvent-free laminating adhesives (adhesives that can be applied at 100% solids and contain neither organic solvents nor water) have significant advantages: they can be applied and operated at very high line speeds because there is no solvent and water that must be removed from the adhesive during the drying step. Typical line speeds for solvent-free adhesives are 900 to even 2000 feet per minute, which is not possible for solvent-based and water-based laminating adhesives. Thus, solventless laminating adhesives have significant advantages over solvent-based or water-based adhesives.

Some solventless polyurethane laminating adhesives must be heated to 100 ℃ to obtain a viscosity suitable for use in laminated packaging materials. These high temperatures are difficult to achieve and control and are not energy efficient. In order to reduce the application temperature, the molecular weight of the first component polyurethane prepolymer can be reduced, but the missing molecular weight must be restored by adding another component (typically a blend of polyols) to the adhesive mixture. The application temperature of these modified polyurethane laminating adhesives can be reduced to about 40 ℃.

The cured adhesive must provide suitable peel strength at room temperature and elevated temperatures (elevated temperature) encountered during food packaging, processing and supply to prevent delamination and contain the food product. The nature of the cured adhesive must also be unaffected by contact with the food product.

There are many regulations governing the use of flexible packaging materials in food packaging applications. Regulations, of course, require that the food package be safe when in contact with the food. Migration of the binder component (e.g., unreacted isocyanate monomer) into the food product is a problem. The excess isocyanate in the laminating adhesive can react with moisture in the packaged product to form primary aromatic amines. The U.S. FDA requires that the primary aromatic amine concentration in flexible packaging materials for food contact be below the detection limit (2 parts per billion (ppb) when tested by migration testing (also known as BfR test method)). One solution is to keep the flexible packaging material in a stored state until the adhesive component has been fully reacted. After the adhesive component has fully reacted, the flexible packaging material is formed into a pouch. Unfortunately, in the case of laminating adhesives using lower molecular weight prepolymers and polyols, this can take a long time, up to several weeks, and involve storage of large amounts of expensive laminates before they can be used.

It is also desirable to use naturally derived materials. This is advantageous in reducing sustainability concerns and also in eliminating dependence on petroleum derived materials. Polylactic acid (PLA) is a naturally derived material that is available in industrial grade at a reasonable price. PLA is currently used for bags and films. Medical grade has been widely used in medical applications where biocompatibility and long-term biodegradability are required. However, current PLA films are not suitable for use in food packaging applications because they lack acceptable strength, elongation, and food resistance.

U.S. patent publication No. 2017/0002240 discloses an attempt to laminate adhesives comprising naturally derived materials. However, this publication mentions the use of OPP/OPP and PET/PE laminates only, and does not mention adhesion to other commercially important substrates. The disclosure also does not mention other important properties of the laminating adhesive, such as heat seal strength. Furthermore, the polyol blends disclosed therein may phase separate during storage and the cured adhesives may not be sufficiently resistant to many foods for use in some food packaging applications.

Similarly, U.S. patent publication No. 2015/019635 discloses the use of polylactic acid reaction products as an ingredient in OH component blends for pressure sensitive adhesives. The properties of the disclosed adhesives are not suitable for use as laminating adhesives in soft food packaging.

It is desirable to provide a laminating adhesive comprising naturally derived materials.

It is also desirable to provide a laminating adhesive comprising naturally derived materials wherein the cured adhesive can provide suitable adhesive strength at room temperature and elevated temperatures to contain food products. The cured adhesive properties must also have improved adhesive strength after contact with food products.

It is also desirable to provide a laminating adhesive comprising a naturally derived material wherein the cured adhesive has improved adhesive strength upon contact with food products.

Disclosure of Invention

The present disclosure provides a two-component laminating adhesive comprising component a and component B. Component a comprises an isocyanate-functional compound. Component B comprises a specific mixture of polyols, wherein at least one of said polyols comprises the transesterification product of a polymeric polylactic acid with a natural oil.

In one embodiment, component B comprises a specific mixture of polyols, wherein at least one of the polyols contains the transesterification product of a polymer polylactic acid with a glycol and a natural oil.

The disclosed component B comprising the transesterification product allows the user to increase sustainability at a cost comparable to petroleum-based laminating adhesives. In combination with a suitable isocyanate component, it also provides the heat resistance, product resistance and adhesive strength desired to produce flexible packages for food.

In one embodiment, the flexible packaging material is formed by combining and mixing components a and B to form a laminating adhesive. The mixed adhesive is disposed onto the selected film using known equipment, the film is laminated and the adhesive is cured to form the flexible packaging material.

The disclosed compounds include any and all isomers and stereoisomers. In general, the disclosed compositions can be alternatively (alternately) formulated to comprise, consist of, or consist essentially of any suitable component disclosed herein. The disclosed compositions may additionally or alternatively be formulated to be free or substantially free of any component, material, ingredient, adjuvant, or substance (specie) used in the prior art compositions or that is not otherwise necessary to achieve the disclosed function and/or purpose.

The word "about" or "approximately" as used herein in connection with a numerical value refers to a value of + -10%, preferably + -5%, more preferably + -1% or less.

Drawings

FIG. 1 is a GPC chromatogram comparing two transesterified polyester polyol reaction products with a comparative polyol reaction product.

The specific embodiment is as follows:

percentages used herein are by weight unless specifically described otherwise. Molecular weights as used herein are number average molecular weights (Mn) unless specifically described otherwise. Mg as used herein means milligrams, g means grams; mol means mole; mmol means millimoles; ml means milliliter, L means liter; ga means gauge. The term "OH number" refers to the hydroxyl number of the polymer and is defined as the milligrams of potassium hydroxide required to neutralize acetic acid absorbed (take up) when 1 gram of the test polymer containing free hydroxyl groups is acetylated. Room temperature is 20 to 25 ℃ at ambient indoor humidity.

The disclosed flexible packaging adhesive in a ready-to-use form comprises a substantially homogeneous mixture of component a and component B. The components a and B are stored separately and mixed in a predetermined ratio just before use. Mixing the components initiates a relatively rapid reaction between the isocyanate groups in component a and the OH groups of the polyol in component B.

Component A

Component a comprises at least one compound having two or more terminal isocyanate groups per molecule. The isocyanate groups are typically free-NCO groups, but may also be blocked or masked-NCO groups. In one embodiment, component a is prepared using one or more polyisocyanates. Preparation from … … means that component a may comprise the one or more polyisocyanates, or may comprise the reaction product of the one or more polyisocyanates, or may comprise both. One embodiment of component a uses one or more isocyanate-functional polyurethane prepolymers. In the context of the present disclosure, a polyurethane prepolymer is, for example, a compound resulting from the reaction of a polyol component (or other active hydrogen functionalized compound) with at least one polyisocyanate having a functionality of at least 2. The term "polyurethane prepolymer" includes not only compounds having a relatively low molecular weight (e.g., formed from the reaction of a polyol with an excess of polyisocyanate), but also oligomeric or polymeric compounds. Likewise the term "polyurethane prepolymer" includes compounds formed, for example, by the reaction of a tri-or tetra-polyol with a molar excess of polyisocyanate relative to the polyol.

The excess unreacted polyisocyanate monomer may optionally be removed from the initially obtained polyurethane prepolymer reaction product by any known method (e.g., distillation) to provide a prepolymer having a desirably low level of polyisocyanate monomer (e.g., less than 1 weight percent).

Polyurethane prepolymers are generally prepared by reacting at least one polyisocyanate (preferably a diisocyanate) and at least one component (typically a polyol component) having a plurality of functional groups that are reactive with isocyanate groups. The molecular weight can be controlled at least approximately by the ratio of OH groups to isocyanate groups.

The polyol component used to prepare the polyurethane prepolymer may contain only one polyol, although a mixture of two or more polyols may also be used as the polyol component. By polyhydric alcohol is meant a polyfunctional alcohol, i.e., a compound having more than one OH group in the molecule. These polyols are, for example, aliphatic alcohols having from 2 to 4 OH groups per molecule. The OH groups may be primary or secondary. Examples of suitable aliphatic alcohols include ethylene glycol, propylene glycol, 1, 4-butanediol, 1, 5-pentanediol, 1, 6-hexanediol, 1, 7-heptanediol, 1, 8-octanediol and their higher homologs or isomers, for example in the form of stepwise extending the hydrocarbon chain by one CH each ₂ The groups are obtained or by introducing branches into the carbon chain. Likewise, suitable are higher polyfunctional alcohols, for example glycerol, trimethylolpropane, pentaerythritol and also the oligoethers of the substances themselves or mixtures of two or more of the ethers with one another.

As polyol component it is additionally possible to use the reaction product of a low molecular weight polyfunctional alcohol with an alkylene oxide, known as polyether polyol. The alkylene oxide preferably has 2 to 4 carbon atoms. Suitable examples are reaction products of ethylene glycol, propylene glycol, isomerised butanediol, hexanediol or 4,4' -dihydroxy-diphenylpropane with ethylene oxide, propylene oxide or butylene oxide, or with mixtures of two or more thereof. Also suitable are reaction products of polyfunctional alcohols (e.g., glycerol, trimethylolethane or trimethylolpropane, pentaerythritol, sugar or sugar alcohols, or mixtures of two or more thereof) with the alkylene oxides to form polyether polyols. Particularly suitable polyether polyols are those having a molecular weight of from about 100 to about 10,000, preferably from about 200 to about 5,000. Likewise suitable as polyol component are polyether polyols, for example formed by polymerization of, for example, tetrahydrofuran.

The polyether polyols may be synthesized by reacting starting compounds having active hydrogen atoms with alkylene oxides using methods known to those skilled in the art: the alkylene oxide is, for example, ethylene oxide, propylene oxide, butylene oxide, styrene oxide, tetrahydrofuran or epichlorohydrin or a mixture of two or more thereof. Examples of suitable starting compounds are water, ethylene glycol, 1, 2-propylene glycol or 1, 3-propylene glycol, 1, 4-butanediol or 1, 3-butanediol, 1, 6-hexanediol, 1, 8-octanediol, neopentyl glycol, 1, 4-hydroxymethylcyclohexane, 2-methyl-1, 3-propanediol, glycerol, trimethylolpropane, hexane-1, 2, 6-triol, butane-1, 2, 4-triol, trimethylolethane, pentaerythritol, mannitol, sorbitol, methylglycoside, sugar, phenol, isononyl phenol, resorcinol, hydroquinone, 1, 2-tris (hydroxyphenyl) ethane or 1, 2-tris (hydroxyphenyl) ethane, ammonia, methylamine, ethylenediamine, tetramethylene amine or hexamethyleneamine, triethanolamine, aniline, phenylenediamine, 2, 4-diaminotoluene and 2, 6-diaminotoluene and polyphenyl polymethylene polyamines (obtainable, for example, by aniline-formaldehyde condensation), or mixtures of two or more thereof.

Likewise suitable for use as the polyol component are polyether polyols which have been modified with vinyl polymers. Such products can be obtained, for example, by polymerizing styrene or acrylonitrile or mixtures thereof in the presence of polyether polyols.

Polyester polyols having a molecular weight of about 200 to about 10,000 are also suitable as the polyol component. Thus, for example, polyester polyols formed by the reaction of low molecular weight alcohols, in particular ethylene glycol, diethylene glycol, neopentyl glycol, hexanediol, butanediol, propanediol, glycerol or trimethylolpropane, with caprolactone can be used. Likewise suitable as polyfunctional alcohols for preparing the polyester polyols are 1, 4-hydroxymethyl cyclohexane, 2-methyl-1, 3-propanediol, but-1, 2, 4-triol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, dibutylene glycol and polytetramethylene glycol.

Further suitable polyester polyols are those which can be prepared by polycondensation. For example, difunctional and/or trifunctional alcohols may be condensed with sub-stoichiometric amounts of di-and/or tricarboxylic acids, or reactive derivatives thereof, to form polyester polyols. Examples of suitable dicarboxylic acids are: adipic acid or succinic acid and their higher homologs having not more than 16 carbon atoms; unsaturated dicarboxylic acids, such as maleic acid or fumaric acid, and aromatic dicarboxylic acids, in particular isomeric phthalic acids (e.g. phthalic acid, isophthalic acid or terephthalic acid). Examples of suitable tricarboxylic acids are citric acid or trimellitic acid. These acids may be used alone or as a mixture of two or more thereof. Particularly suitable in the context of the present disclosure are polyester polyols formed from glycerol and at least one of the dicarboxylic acids, which have a residual OH group content. Particularly suitable alcohols are hexanediol, ethylene glycol, diethylene glycol or neopentyl glycol or mixtures of two or more thereof. Particularly suitable acids are isophthalic acid or adipic acid or mixtures thereof.

The high molecular weight polyester polyol includes: for example, the reaction product of a polyfunctional alcohol, preferably a difunctional alcohol (together with a small amount of a trifunctional alcohol, if appropriate), and a polyfunctional carboxylic acid, preferably a difunctional carboxylic acid. Instead of the free polycarboxylic acids, it is also possible to use (if possible) the corresponding polycarboxylic anhydrides or corresponding polycarboxylic esters with alcohols preferably having from 1 to 3 carbon atoms. The polycarboxylic acid may be aliphatic, cycloaliphatic, aromatic or heterocyclic or both. If appropriate they may be substituted, for example by alkyl, alkenyl, ether or halogen. Examples of suitable polycarboxylic acids include succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, tetrachlorophthalic anhydride, methanotetrahydrophthalic anhydride, glutaric anhydride, maleic acid, maleic anhydride, fumaric acid, dimer fatty acids or trimer fatty acids, or mixtures of two or more thereof. If appropriate, smaller amounts of monofunctional fatty acids may be present in the reaction mixture.

If appropriate, the polyester polyols may contain a small proportion of carboxyl end groups. Polyester polyols obtainable from lactones (e.g. epsilon-caprolactone) or hydroxycarboxylic acids (e.g. omega-hydroxycaproic acid) can likewise be used.

Polyacetal and polyester ether polyols are likewise suitable as polyol components. Polyacetal means a compound obtainable by reacting a diol with an aldehyde, for example obtainable by condensing diethylene glycol or hexanediol or mixtures thereof with formaldehyde. Polyacetal useful in the context of the present disclosure may likewise be obtained from the polymerization of cyclic acetals.

Further suitable polyols include polycarbonates. Polycarbonates may be obtained, for example, by reacting diols (e.g., propylene glycol, 1, 4-butanediol or 1, 6-hexanediol, diethylene glycol, triethylene glycol or tetraethylene glycol, or mixtures of two or more thereof) with diaryl carbonates (e.g., diphenyl carbonate) or phosgene.

The polyisocyanates useful in component a are not limited and include compounds having two or more reactive isocyanate groups or mixtures of compounds having an average of two or more reactive isocyanate groups.

Some useful polyisocyanates include: for example, 1, 5-naphthylene diisocyanate, diphenylmethane diisocyanate (MDI), hydrogenated MDI (H) ₁₂ MDI), xylylene Diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), 4' -diphenyldimethylmethane diisocyanate, di-and tetra-alkylene diphenylmethane diisocyanate, 4' -dibenzyl diisocyanate, 1, 3-phenylene diisocyanate, 1, 4-phenylene diisocyanate, isomers of Toluene Diisocyanate (TDI), 1-methyl-2, 4-diisocyanatocyclohexane, 1, 6-diisocyanato-2, 4-trimethylhexane, 1, 6-diisocyanato-2, 4-trimethylhexane 1-isocyanatomethyl-3-isocyanato-1, 5-trimethylcyclohexane (IPDI), chlorinated and brominated diisocyanates, phosphorus-containing diisocyanates, 4' -diisocyanatophenyl perfluoroethane, tetramethoxybutane 1, 4-diisocyanate, butane 1, 4-diisocyanate, hexane 1, 6-diisocyanate (HDI), dicyclohexylmethane diisocyanate, cyclohexane 1, 4-diisocyanate, ethylene diisocyanate, diisocyanatoethyl phthalate; and diisocyanates having reactive halogen atoms, e.g. 1-chloromethylphenyl 2, 4-diisocyanate, 1-bromomethylphenyl 2, 6-diisocyanate, 3-bisChloromethyl ether 4,4' -diphenyl diisocyanate.

Diphenylmethane diisocyanate (MDI) can be obtained in three isomers: 4,4 '-diphenylmethane diisocyanate (4, 4' -MDI), 2,4 '-diphenylmethane diisocyanate (2, 4' -MDI) and 2,2 '-diphenylmethane diisocyanate (2, 2' -MDI). Mixtures of two or more of these isomers may be used for some or all of the polyisocyanates. Alternatively, one or more of these isomers may be excluded.

Modified forms of diphenylmethane diisocyanate may be used for some or all of the polyisocyanates. Examples of useful modified MDI include, for example, carbodiimide-modified diphenylmethane diisocyanate (carbodiimide-modified MDI), allophanate-modified diphenylmethane diisocyanate (allophanate-modified MDI), biuret-modified diphenylmethane diisocyanate (biuret-modified MDI), polymeric MDI, and combinations thereof.

Component a is preferably formulated to have an isocyanate functionality of 2 or greater. The use of component a having an isocyanate functionality of less than 2 is unlikely to provide a laminating adhesive with the desired properties.

Component a is preferably formulated to have a viscosity of no greater than about 10,000cps (more preferably no greater than about 5000cps, most preferably no greater than about 3500 cps) at 25 ℃ and a viscosity of no greater than about 2500cps (more preferably no greater than about 2000 cps) at 60 ℃. The polyurethane prepolymers used in component a may generally have a molecular weight of 500 to 27,000, or 700 to 15,000, or 700 to 8,000 g/mol.

Component B

Component B comprises the transesterification product of the polymer polylactic acid with natural oil. In some embodiments, component B comprises a mixture of polyols comprising the transesterification product of the polymer polylactic acid with natural oil and a different polyol. In some embodiments, component B comprises a mixture of polyols comprising the transesterification product of polymeric polylactic acid with natural oil, a different polyol, and a high OH functionality polyol product.

Transesterification processes for various reactive components are known in the art. Throughout the transesterification reaction, an alcohol is reacted with an ester in the presence of a catalyst, and one R group on the ester is exchanged with an R group on the alcohol: r '-OH+R' -O-C (O) -R.fwdarw.R '-OH+R' -O-C (O) -R. The transesterified polylactic acid polymer has desirable improved properties compared to polylactic acid, such as: is liquid or waxy solid at room temperature, and has improved solubility in various solvents.

The following is a general description of transesterification processes that may be used herein. The high molecular weight polylactic acid polymer and optional glycol and/or transesterification catalyst are mixed to form a reaction mixture, and the reaction mixture is heated to a temperature below the degradation temperature of the reaction mixture components to form a molten reaction mixture. At least one natural oil is added to the molten reactants. Initially, the molten reaction mixture and natural oil are mixed to form a bilayer mixture. The components are mixed at elevated temperature until substantially homogeneous. The temperature of the substantially homogeneous mixture is raised to a temperature high enough to effect transesterification. The substantially homogeneous reaction mixture is maintained at or above this temperature until transesterification is complete to the desired degree. Once transesterification is completed to the desired extent, the reaction mixture is cooled to a temperature convenient for handling and the transesterified polylactic acid reaction product is collected. Typically, the transesterification process is carried out until the reaction mixture forms a clear and homogeneous monolayer product.

The transesterification process breaks down the high molecular weight polylactic acid polymer into PLA oligomers of much lower molecular weight, breaks down the natural oil into the lower molecular weight components fatty acids and glycerin, and randomly reacts and combines these lower molecular weight components to form a variety of PLA polyols. Fatty acids derived from natural oils were found as side chains attached to transesterified polylactic acid products. The diol and the released glycerol are found at the end of the transesterified polylactic acid product or they link smaller polylactic acid oligomers together. The optional diol enables adjustment of the OH number and molecular weight of the transesterified polylactic acid product. Further details of the transesterification process can be found in International publication number WO 2017/136373, the contents of which are incorporated herein by reference.

The number average molecular weight of the high molecular weight polylactic acid polymer is not particularly limited, and preferably includes polylactic acid having a number average molecular weight of 2,000 to 200,000, preferably 10,000 to 100,000, and more preferably about 60,000 to 100,000.

Natural oil refers to oil derived from nature. Useful natural oils include, for example: soybean oil, castor oil, canola oil, sunflower oil, safflower oil, corn oil, peanut oil, almond oil, olive oil, coconut oil, palm oil, tall oil, and mixtures thereof.

An optional diol is any structure comprising two reactive hydroxyl groups and having a molecular weight of about 50 to about 2000 daltons. The optional diol is typically not a natural oil. Optional diols useful in the reaction of the present invention include: diethylene glycol, polypropylene glycol having a molecular weight of 400-2000 daltons, polyethylene glycol having a molecular weight of 400-2000 daltons, neopentyl glycol, propylene glycol, dipropylene glycol, hexylene glycol, ethylene glycol, 2-methyl-1, 3-propanediol, butylene glycol and polytetrahydrofuran. When glycerol links two polylactic acid chains, the additional hydroxyl groups may also be sites for transesterification reactions. The use of an appropriate amount of diol will result in an OH-terminated distribution of the polyester with glycerol and fatty acids incorporated into the polylactic acid polymer. The side chain fatty acids reduce the viscosity of the resulting polylactic acid polymer, while the polylactic acid backbone provides rigidity.

The transesterification catalyst may be selected from a variety of catalysts including: phosphoric acid and esters thereof, sulfonic acids such as p-toluenesulfonic acid; and sulfuric acid. In addition, the base-catalyzed reaction may be carried out by using as catalysts: alkali metal alkoxides, e.g. sodium methoxide (CH) ₃ ONa); alkali metal hydroxides, such as KOH or NaOH; or dibutyltin dilaurate; or tin octoate. In some embodiments, no transesterification catalyst is used. Preferred transesterification catalysts are titanium alkoxides, such as tetrabutyl titanate (IV).

Preferably, the transesterified polylactic acid component B product has a hydroxyl number of from 80 to 200mg KOH/g, more preferably from 115 to 145mg KOH/g and even more preferably from 120 to 140mg KOH/g.

Component B may optionally comprise a polyol different from the transesterification product of the polymer polylactic acid with natural oil. The polyol optionally present may be a polyether polyol or a polyester polyol. The optional polyol may be derived from a natural oil, but is typically not derived from a natural oil.

Component B may optionally comprise a high OH functionality polyol product. High OH functionality polyol products are described in U.S. patent publication No. 2006/0105188 to Simons, the contents of which are incorporated herein by reference. The high OH functionality product contains an average of two or more primary hydroxyl groups, and preferably also contains an average of two or more secondary hydroxyl groups. The high OH functionality polyol product is obtained by a two-step process comprising reacting a first polyol comprising predominantly secondary hydroxyl groups with a stoichiometric excess of a reactant selected from the group consisting of polyacids, polyacids anhydrides, polyacid esters and polyisocyanates to form an intermediate comprising at least about two terminal functional groups per molecule selected from the group consisting of isocyanates, carboxylic acids and carboxylic acid esters. The intermediate is reacted with a stoichiometric excess of a second polyol containing predominantly primary hydroxyl groups to form a high OH functionality polyol product. The reaction of these components in a single step will not provide a high OH functionality polyol product that is acceptable for use in a laminating adhesive.

Preferably, the weight percentage of component B derived from the transesterification product of the polymeric polylactic acid with natural oil is 50 to 85 wt%, more preferably 50 to 80 wt%, based on the total component B weight. Preferably, the weight percentage of the component B product derived from natural oil in the final product is 13-30 wt.%, based on the total component B weight. When an optional diol is used, the weight percent of component B product derived from the optional diol in the final product is from 2 to 36 weight percent, based on the total component B weight. Different diols, if present, may be used in the range of 0 to 50 wt.%, based on the total component B weight. As used herein, the renewable content of a component is the weight percent of that component derived from a natural source. The renewable content of the component B product is in the range of at least 70%. Component B preferably has a viscosity of 3,000 to 20,000cps at 25 ℃, more preferably 5,000 to 18,000cps at 25 ℃. Component B preferably has a viscosity of about 2700cps at 40 ℃ and 1100cps at 50 ℃.

The amounts of component a and component B used in the laminating adhesive system are generally adjusted to provide a weight ratio of the adhesive composition in one embodiment of the invention of about 1:1 to 10:1 and in another embodiment within about 1.05:1 to about 5: NCO in the range of 1: active hydrogen (OH) equivalent ratio. Typically, the free isocyanate content (prior to any reaction of component a and component B) is from about 1% to about 25% by weight based on the total weight of the two-component adhesive. The weight ratio of component a to component B may vary within wide limits, with the optimum ratio depending on the composition of each of component a and component B.

The mixture of component a and component B when initially mixed has a viscosity of about 600cps to about 2500cps (more preferably about 800cps to about 1500 cps) at the application temperature. The viscosity of the mixed adhesive above 5,000cps at application temperature is difficult or impossible to operate with conventional solventless lamination equipment. Typical application temperatures for flexible packaging lamination are about 40 ℃, although higher or lower application temperatures may be useful in some applications.

Typically, the mixed adhesive will have a pot life of at least about 15 minutes and more preferably at least about 30 minutes. Pot life is the time required for the viscosity of the mixed adhesive to increase from the initial viscosity to twice the original viscosity after mixing component a and component B and maintaining at a temperature of 40 ℃.

If appropriate, the two-component laminating adhesive may optionally comprise, in addition to component a and component B, one or more further additives conventionally used in flexible packaging laminating adhesives. The additives may, for example, comprise no more than about 10% by weight of the total two-component adhesive. Additives may be present in either of components a and B. Optional additives that may be used in the context of the present disclosure include solvents, water, catalysts, curing agents, accelerators, plasticizers, stabilizers, antioxidants, light stabilizers, fillers, dyes, pigments, fragrances, preservatives, or mixtures thereof. Components A and/or B may also be free of any or all of these additives.

The film or films to be coated and adhered to each other using the two-component adhesive formulation may be composed of any material known in the art to be suitable for use in flexible packaging laminates, including polymeric and metallic materials and papers (including treated or coated papers). Thermoplastic polymers are particularly preferably used as at least one layer. The materials selected for the various layers in the flexible packaging laminate may be the same, but are typically different materials, wherein the different materials are selected to achieve a particular desired combination of properties, such as mechanical strength, tear resistance, elongation, puncture resistance, flexibility/rigidity, gas and moisture permeability, grease permeability, heat sealability, adhesion, optical properties (e.g., transparent, translucent, opaque), formability, marketability (marketability), and relative cost. Each layer may be a pure polymer or a blend of different polymers. Polymeric layers are often formulated with the following materials to improve certain layer properties: colorants, anti-slip, anti-blocking (anti-block) and antistatic processing aids, plasticizers, lubricants, fillers, stabilizers, and the like.

Particularly preferred polymers for use as layers include, but are not limited to: polyethylene (including Low Density Polyethylene (LDPE), medium Density Polyethylene (MDPE), high density polyethylene (HPDE), high molecular weight high density polyethylene (HMW-HDPE), linear Low Density Polyethylene (LLDPE), linear medium density polyethylene (LMPE)), polypropylene (PP), oriented polypropylene; polyesters such as poly (ethylene terephthalate) (PET) and poly (butylene terephthalate) (PBT); ethylene-vinyl acetate copolymer (EVA), ethylene-acrylic acid copolymer (EAA), ethylene-methyl methacrylate copolymer (EMA), ethylene-methacrylate (ionomer), hydrolyzed ethylene-vinyl acetate copolymer (EVOH), polyamide (nylon), polyvinyl chloride (PVC), poly (vinylidene chloride) copolymer (PVDC), polybutylene, ethylene-propylene copolymer, polycarbonate (PC), polystyrene (PS), styrene copolymer, high Impact Polystyrene (HIPS), acrylonitrile-butadiene-styrene polymer (ABS), acrylonitrile copolymer (AN), polyester, polyamide (nylon), polylactic acid (PLA) and regenerated cellulose film (cellophane).

One or both surfaces of the polymer film may be treated or coated, if desired. For example, a polymer film may be metallized by depositing a thin metal vapor (e.g., aluminum) onto the surface of the film. The metallization can improve the barrier properties of the final laminate. The polymer film surface may also be coated with anti-fog additives or the like, or pretreated with electricity or corona discharge, or ozone or other chemicals to improve its adhesive acceptance (adhesive receptivity). A coating of an inorganic oxide (e.g., siOx or AlOx) may also be present on the polymer surface (e.g., a PET film coated with SiOx or AlOx).

One or more layers in the laminate may also comprise a metal film or foil, such as aluminum foil or the like. The metal foil preferably has a thickness of about 5-100 μm.

The individual films comprising the laminate may be prepared in widely varying thicknesses (e.g., about 5 to about 200 microns). The films, foils, and laminating adhesive formulations can be assembled into a laminate using any one or more of several conventional procedures known in the art for this purpose. For example, the adhesive formulation may be applied to the surface of one or both of the two films/foils by means of extrusion, brush, roller, doctor blade, spray coating, etc., the film/foil surfaces with the adhesive composition are brought together and passed through a set of rollers (often referred to as nip rollers) which press the films/foils together with the adhesive composition between the films/foils. The resulting laminate may be rolled or wound onto a reel to enable the adhesive to fully cure prior to further processing. The adhesive may be applied by conventional techniques, such as by a multi-roll application station (multi-roll application station).

One typical method for applying the adhesive composition to a substrate (e.g., film or foil) is by using a series of smooth-surfaced rubber and steel coating rolls (transfer rolls) on a solvent-free adhesive laminator. The components of the adhesive were mixed by using the following equipment: the correct amounts of the components can be automatically measured and mixed and the resulting mixture delivered to the metering/mixing/dispensing (MMD) equipment of the laminator. The mixed adhesive is deposited on the first two rolls and metered through the remaining rolls (typically, 3 to 5 rolls) in the application station. The flow characteristics of the adhesive composition may be improved by heating the first two rolls to a temperature of about 35 to about 60 ℃. Typically, the final applicator roll is heated to a temperature of about 40 to about 60 ℃. Changes to these temperatures may be required depending on the line speed, substrate and roll size.

The coating weight of the adhesive formulation when applied to the surface of the film layer may be in the range of about 0.12 to about 3.1lbs./ream.ft. For solvent-free lamination, more typically in the range of about 0.8 to about 1.4lbs./ream sq.ft. And in the range of 1.2-3.5lbs./ream for solvent-based adhesive lamination.

The second film or foil substrate is pressed by one or more rollers onto the substrate to which the adhesive has been applied. The nip temperature (nip temperature) may be adjusted as desired depending on the line speed, thickness of the laminate, reactivity of the adhesive and other characteristics, and the substrate being laminated, but temperatures of about 45 ℃ to about 90 ℃ are typically suitable.

It may be desirable to heat the laminate at an elevated temperature (e.g., about 40 ℃ to about 100 ℃) to promote adequate curing of the adhesive composition. Alternatively, the adhesive composition may be curable at about room temperature (e.g., about 20 ℃ to about 25 ℃) or higher for a period of about 1 day to about 14 days.

In general, it is believed that the disclosed adhesive compositions are mostly chemically cured by reacting the components of the formulation containing isocyanate groups with the components containing hydroxyl or other active hydrogen groups. However, partial curing can also take place by reaction of the isocyanate groups in component a with moisture inherently present on the film or foil surface. Curing by reaction of the isocyanate groups in component a with moisture alone is undesirable and should be avoided.

Laminates prepared according to the present disclosure may be used for packaging purposes in the same manner as conventional or known soft laminate packaging films. The laminate is particularly suitable for forming a soft bag-like container that can be filled with food and sealed. For example, two rectangular or square laminate sheets may be overlapped in a desired configuration or arrangement; preferably, two layers of two sheets opposite each other can be heat sealed to each other. The three peripheral portions of the overlapping assemblies are then heat sealed to form a bag. The heat sealing can be easily accomplished by means of a heating rod, a heating knife, a heating wire, a pulse sealer, an ultrasonic sealer, or an induction heat sealer. One peripheral portion remains open to enable filling of the bag with product.

The food product is then packed in the thus formed bag through the open peripheral portion. If necessary, the gas (e.g., air) harmful to the food is removed by known means such as vacuum degassing, heat packing, boiling degassing, or steam spraying or container deformation. The bag opening is then heat sealed. The packaged bag may be heated after a period of time.

Adhesives used to adhere films to flexible packages must possess a number of commercially beneficial properties. These properties will vary depending on the intended use of the flexible package. The cured reaction product of the adhesive must migrate little or no from the package into the packaged product. For low stress applications, the cured reaction product of the laminating adhesive must have a minimum room temperature adhesive strength to ordinary laminated film materials of 200 to 300 grams/inch. For higher stress applications, the cured reaction product of the laminating adhesive must have a minimum room temperature adhesive strength to ordinary laminated film materials of 400 grams/inch or greater. The most preferred results are: the cured reaction product on top of the laminating adhesive has sufficient room temperature adhesive strength to the ordinary laminating film material to render the laminating film ineffective prior to the adhesive. The cured reaction product of the laminating adhesive must retain most of this room temperature adhesive strength to the conventional laminated film material after exposure to the packaged food product. For some applications, the cured reaction product of the laminating adhesive must retain a substantial portion of this adhesive strength after exposure to elevated temperatures.

Examples:

the following materials were used in the examples.

DEG diethylene glycol.

PLA is available as 3052D from Nature eworks LLC as polylactic acid polymer Mn 85000 daltons.

Tetrabutyl titanate catalyst is available as Tyzor TPT from Dorf Ketal.

Castor oil is available as T31 oil from Eagle Specialty Products.

Fuller P-A is an isocyanate functional material available from H.B.Fuller.

Liosol LA 3817, a solvent-based isocyanate functional material available from Henkel Corporation comprising 80% solids by weight in ethyl acetate solvent, has an nco% of about 2.8%.

Liofol LA 7660, an isocyanate functional material available from Henkel Corporation having an NCO% of about 16%.

Liofol LA 7773, an isocyanate functional material available from Henkel Corporation having an NCO% of about 16%.

Polyethylene terephthalate (PET GP) is a typical 48ga polyester film used for the outer layer of food packaging laminates. It can be used as a support for a less strong film, such as an aluminum foil. It is usually printed on the side facing the inside of the package.

PET Met is a 48-gauge polyester with a very thin aluminum layer by vacuum vapor deposition

PET-foil is 48-gauge polyester laminated to 0.0035ga aluminum foil with a solvent-based commercial adhesive

RLS OPP is an oriented polypropylene film of about 75 gauge.

High Slip PE is a polyethylene film containing about 1000ppm of Slip agent (e.g., erucamide) to facilitate handling properties. Including different thicknesses (1 mil and 2 mils) commonly used in the marketplace.

Low Density Polyethylene (LDPE) is a polymer having a density of about 0.910 to about 0.925g/cm ³ Is a homopolymer of ethylene.

Laminate combination 1 was 1000ppm PET GP (48 ga)/adhesive/High Slip PE (2 mil).

Laminate combination 2 was PET GP (48 ga)/adhesive/LDPE (1 mil).

Laminate combination 3 was 1000ppm PET Met (48 ga)/adhesive/High Slip PE (2 mil).

Laminate combination 4 was RLS OPP (75 ga)/adhesive/RLS OPP (75 ga).

Laminate combination 5 was 1000ppm of PET-foil/adhesive/High Slip PE (2 mil).

Laminates were prepared by coating each of the prepared adhesives with Nordmeccanica Labo Combi at a coat weight of about 1.2 lbs./ream.

The viscosity was measured at 25℃by using a Brookfield viscometer.

The bond strength was tested by the time required to prepare the flexible packaging laminate material and cure the material. Samples of 1 inch x 4 inch to 6 inches were cut from the bag and tested for adhesive strength via a tensile strength tester at room temperature or at the desired elevated temperature, with failure modes noted. This is a T-peel test in which the tail of the laminate is held at 90 degrees to the end being pulled.

The heat seal bond strength was tested according to ASTM F88 Seal Strength of Flexible Barrier Materials. Typically, the laminated samples are cut into test pieces 1 inch wide by about 6-8 inches long. The test piece was folded so that the sealing film was inside and the total folded length was 3-4 inches. A heat seal is formed in the folded material. A tensile tester with a 100lb load cell was used and each leg (leg) of the test piece was clamped in the tensile tester. The test piece was placed laterally in the center of the clamp. The test piece is aligned in the clamp such that the sealing line is perpendicular to the pulling direction. The heat seals were tested at a clamp release rate of 8-12 inches/minute. The test material failed and the force (strength) values and pattern of test piece failure were recorded.

The product resistance was tested by preparing a flexible packaging laminate material and allowing the material to cure for the time required. A 4 inch x 4 inch pouch was prepared from the cured laminate and about 30ml of the test food (2 g for coffee and flavored coffee samples) was sealed therein. The sealed bag was aged at 60 ℃ for 100 hours. At the end of the aging period, 1 inch by 4 inch to 6 inch samples of the adhesive area were cut from the bag and tested for adhesive strength, with failure modes recorded. The test food products included water, tomato paste, mayonnaise, vegetable oil, 1-1-1 sauce (1:1:1 mixture of tomato paste, vinegar and vegetable oil), unflavored coffee and hazelnut flavored coffee.

Failure modes and abbreviations thereof are:

elongation-E; when one or both of the substrates are elongated during testing.

SF-material failure; one or both laminated films failed.

P-stripping; when the laminate is allowed to separate the entire length of the test strip without tearing or cracking either of the two substrates.

SS-splitting of the raw material; upon failure of either of the two substrates after the first inch of the test strip

MT-metal transfer; the metallized layer peels away from the original metallized film and remains adhered to the other film.

Z-zipper; when the failure has alternating high intensity, low intensity, high intensity, low intensity modes

P-MT-stripping and metal transfer;

P/E-N-peel and stretch necking (neg);

P/E/N-SS-peeling and elongating necking and splitting of the feedstock

P/Z-peel and slide fastener

Preparation of transesterified polyester polyol product 1:

the round bottom flask was equipped with thermometer, mechanical stirrer, reflux condenser and nitrogen inlet. The flask was charged with 104g of diethylene glycol (DEG) and 555g of high molecular weight PLA polymer. Tetrabutyl titanate (IV) was first dissolved in isopropanol at 0.1g/mL and then 2mL of the tetrabutyl titanate solution was added to the flask. The reaction solution was heated to 150 to 165 ℃ with stirring. When complete melting of the mixture occurred, 155g of castor oil was added to the flask, the temperature was raised to 170-180 ℃ and held for 3 hours. The temperature of the mixture was raised to 190-200 ℃ and maintained for 4 hours. The temperature of the mixture was further raised to 210-220 ℃ and held there for 7 hours or until a clear homogeneous mixture was obtained.

The heating was stopped and the transesterified reaction product was discharged when the temperature was reduced to 50 ℃. This is sample 1.

Sample 1 is a transesterified polyester polyol reaction product having a number average molecular weight of about 935g/mol, an OH number of 125mgKOH/g, a viscosity of 14500cps at 25℃and a weight per gallon of 9.75 lbs/gallon.

Preparation of transesterified polyester polyol product 2:

the round bottom flask was equipped with thermometer, mechanical stirrer, reflux condenser and nitrogen inlet. The flask was charged with 156g dipropylene glycol (DPG) and 509g of high molecular weight PLA polymer. Tetrabutyl titanate (IV) was first dissolved in isopropanol at 0.1g/mL and then 2mL of the tetrabutyl titanate solution was added to the flask. The reaction solution was heated to 150 to 165 ℃ with stirring. When complete melting of the mixture occurred, 134g of soybean oil was added to the flask, the temperature was raised to 170-180 ℃ and held for 3 hours. The temperature of the mixture was raised to 190-200 ℃ and maintained for 4 hours. The temperature of the mixture was further raised to 210-220 ℃ and held there for 7 hours or until a clear homogeneous mixture was obtained. The heating was stopped and the transesterified reaction product was discharged when the temperature was reduced to 50 ℃. This is sample 2.

Sample 2 was a transesterification polyester polyol reaction product having a number average molecular weight of about 772g/mol, an OH number of 127mgKOH/g, and a viscosity of 6200cps at 25 ℃.

Preparation of high OH functionality polyether polyol product 3:

polypropylene glycol (1025 number average molecular weight; 2 equivalents based on hydroxyl groups; 72 wt.% of the total reaction mixture) was reacted with adipic acid alone (4 equivalents based on carboxyl groups; 27 wt.% of the total reaction product) at 238 ℃. The reaction mixture was cooled to 160℃and then glycerol (6 equivalents based on hydroxyl groups; 13% by weight of the total reaction mixture) was added and reacted at 230 ℃. The reaction product was then dried. This is sample 3.

Sample 3 is a high OH functionality polyether polyol product having a functionality of 2-4 and an OH number of about 150; equivalent weight (on hydroxyl basis) 355; the viscosity at 25℃is about 5,000cps. Sample 3 was stable and did not segregate. Sample 3 has at least about two primary hydroxyl groups and at least about two secondary hydroxyl groups.

Preparation of two-component (2K) solvent-free laminating adhesive Ad 1:

loctite Liofol LA 7773 was used as isocyanate functional component A1. 80% by weight of the transesterified polyester polyol sample 1 and 20% by weight of the high-functionality polyether polyol sample 3 were homogeneously mixed. This is polyol component B1.

Component A1 and component B1 were mixed at a ratio of 1.4 parts of component A1 to 1 part of component B1 (representing an NCO/OH equivalent ratio of 1.4/1) to form a curable mixed laminating adhesive Ad1. The soft laminate was prepared by using multiple substrates and curable mixed laminating adhesives at an application temperature of 45 ℃, a coat weight of 1.2lbs/ream, and a nip temperature of 60 ℃. The resulting laminate was tested for adhesive strength and product resistance and the results are shown in the following table.

( Failure mode abbreviation: SF-material failure; p-stripping; SS-splitting of the raw material; P-MT-peel-metal transfer; P/E-N-peel elongation necking; P/E/N-SS-peel elongation neck-stock splitting )

All adhesives and laminates have a strength suitable for various packaging applications.

Product resistance was tested by using bags made from samples of laminates Ad1-1 that had been cured for 9 and 17 days. The results are shown in the following table.

The adhesives and laminates have strength suitable for a variety of packaging applications. Product resistance for hazelnut flavored coffee (very demanding test medium) has mixed results: 318g peel from the 17 day cured laminate and 25g peel from the 9 day cured laminate.

Preparation of two-component (2K) solvent-based laminating adhesive Ad 2:

loctite Liofol LA 3817 was used as isocyanate functional component A2.

80% by weight of the transesterified polyester polyol sample 1 and 20% by weight of the high-functionality polyether polyol sample 3 were homogeneously mixed. This is polyol component B1.

Component A2 and component B1 were mixed at a ratio of 53 parts component A1 to 10 parts component B1 (representing an NCO/OH equivalent ratio of 1.4/1) to form a curable mixed laminating adhesive Ad2. The soft laminate was prepared by using multiple substrates and curable mixed laminating adhesives at an application temperature of 45 ℃, a coat weight of 1.5lbs/ream, and a nip temperature of 60 ℃. The resulting laminate was tested for adhesive strength and product resistance and the results are shown in the following table.

Adhesive Ad2 maintained adhesive strength properties when tested for 21 days. All adhesives and laminates have a strength suitable for various packaging applications.

Bags made from samples of laminates Ad2-1 that had been cured for 9 days and 17 days were used to test product resistance. The results are shown in the following table.

The adhesives and laminates have strength suitable for a variety of packaging applications.

Preparation of two-component (2K) solvent-free laminating adhesive Ad 3:

loctite Liofol LA 7660,7660 was used as isocyanate functional component A3.

100 wt% of the transesterified polyester polyol product sample 1 was used as polyol component B2.

Component A3 and component B2 were mixed at a ratio of 1.4 parts component A3 to 1 part component B2 (representing an NCO/OH equivalent ratio of 1.4/1) to form a curable mixed laminating adhesive Ad3. The soft laminate was prepared by using laminate combination 1 at an application temperature of 40 ℃, a coat weight of 1.2lbs/ream, and a nip temperature of 60 ℃. The soft laminate was cured at 20 ℃ for 16 days.

The adhesives and laminates have strength suitable for a variety of packaging applications. After 48 hours of curing, the adhesive and heat seal had a failure mode of raw material tearing with the desired PET GP (48 ga)/High Slip PE (2 mil) 1000ppm structure.

After 16 days of curing, the AD3-1 samples were tested for product resistance. The results are shown in the following table.

The product resistance after 16 days of curing is essentially absent, which indicates that the soft laminate is not suitable for use in food packaging other than vegetable oils. While these laminates are less suitable for use in food packaging, they are useful in applications where the product is dry or where biodegradability is desired.

Preparation of two-component (2K) solvent-free laminating adhesive Ad 4:

loctite Liofol LA 7660,7660 was used as isocyanate functional component A3.

Component A3 and component B1 were mixed in a ratio of 1.4 to 1 (representing an NCO/OH equivalent ratio of 1.4/1) to form a curable mixed laminating adhesive Ad4. A soft laminate was prepared using 48ga PET as the primary web (web) and laminated to 1000ppm slip 2 mil PE (laminate combination 1). Lamination was completed at an application temperature of 40 ℃, a coat weight of 1.2lbs/ream, and a nip temperature of 60 ℃. The soft laminate was cured at 20 ℃ for 16 days.

The room temperature adhesive strength after 48 hours was measured and the results are shown in the following table.

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The Ad4-1 samples were tested for product resistance after 16 days of curing. The results are shown in the following table.

Product resistance is suitable for some food packaging applications but not as good as AD1 results (in particular water resistance and coffee resistance).

Preparation of two-component (2K) solvent-free laminating adhesive Ad 5:

loctite Liofol LA 7773 was used as isocyanate functional component A1.

The transesterified polyester polyol product was prepared by using the same reactants, amounts of reactants and methods as sample 1 but in a different batch. This is sample 1a. 100 wt% of the transesterified polyester polyol product sample 1a was used as polyol component B2a.

Component A1 and component B2a were mixed at a ratio of 1.4 parts component A1 to 1 part component B2a (representing an NCO/OH equivalent ratio of 1.4/1) to form a curable mixed laminating adhesive Ad5. The soft laminate was prepared by using laminate combination 1 at an application temperature of 40 ℃, a coat weight of 1.2lbs/ream, and a nip temperature of 60 ℃. The soft laminate was cured at 20 ℃ for 14 days. The adhesive strength is shown in the table below.

The adhesives and laminates have strength suitable for a variety of packaging applications. For the 24 hour cured samples, the heat seal failure mode was PET GP (48 ga)/High Slip PE (2 mil) 1000ppm structural stock tear.

Samples of AD5-1 were tested for product resistance after 16 days of curing. The results are shown in the following table.

The product resistance after 16 days of curing is essentially absent, which indicates that the soft laminate is not suitable for use in food packaging other than vegetable oils. While these laminates are less suitable for use in food packaging, they are useful in applications where the packaged product is dry or where biodegradability is desired.

Preparation of two-component (2K) solvent-free laminating adhesive Ad 6:

loctite Liofol LA 7773 was used as isocyanate functional component A1.

80% by weight of the transesterified polyester polyol product sample 2 and 20% by weight of the high functionality polyether polyol product 3 were homogeneously mixed. This is polyol component B3.

Component A1 and component B3 were mixed at a ratio of 1.4 parts of component A1 to 1 part of component B3 (representing an NCO/OH equivalent ratio of 1.4/1) to form a curable mixed laminating adhesive Ad6. The soft laminates were prepared by using laminate combination 1 and curable mixed laminating adhesive Ad6 at an application temperature of 35 ℃, a coating weight of 1.2lbs/ream and a nip temperature of 60 ℃. The resulting laminate was tested for adhesive strength and product resistance and the results are shown in the following table.

Bags made from samples of laminates Ad6-1 that had been cured for 9 days and 16 days were used to test product resistance. The results are shown in the following table.

Adhesive Ad6 maintains adhesive strength when tested with a variety of food products and is suitable for use in a wide range of food packaging applications.

Preparation of a comparative polyol component PC-1 comprising a Natural oil:

comparative polyol component 1 (PC-1) was prepared as described in U.S. patent publication 2017/0002240 to Ostlend et al with respect to polyol component 1.

The OH numbers, acid numbers and viscosities of sample 1a, sample 2 and PC-1 were measured and the results are shown below.

Samples 1a, 2 and PC-1 were compared via GPC. FIG. 1 is a normalized GPC chromatogram (RI detector) of these samples. The following table also shows the data of these GPC analyses.

As shown by GPC in the above Table and FIG. 1, the molecular weights of the three PLA polyols are in the range of 1000 to 1500 g/mol. Samples 1a and 2 were more amorphous in character than PC-1. Samples 1a and 2 had an additional amount of lower molecular weight oligomer compared to PC-1, which made samples 1a and 2 less tacky and easier to process during lamination.

Preparation of comparative two-component (2K) solvent-free laminating adhesive AdPC-1.

Commercially available Fuller P-A (isocyanate functional component) was mixed with the comparative polyol component 1PC-1 in a ratio of 8 parts by weight Fuller P-A to 10 parts by weight PC-1 representing an NCO/OH equivalent ratio of 1.25/1 to form the comparative adhesive AdPC-1. The laminate was prepared with laminate combination 1 (PET GP/adhesive/High Slip PE) using a coating weight of 1.2lbs./ream, an application temperature of 45 ℃ and a nip temperature of 60 ℃. An adhesive was applied to the PET GP film and a High Slip PE film was laminated thereto. This is the comparative sample PC-1-1.

The comparative laminated samples were cured at room temperature after which the samples were tested.

Ad1-1 and Ad6-1 adhesives and laminates have strength suitable for a variety of packaging applications. The comparative AdPC-1-1 adhesives and laminates have adhesive strength at room temperature and elevated temperature that is unsuitable for any food packaging application.

The product resistance was tested by using bags made from samples of laminates Ad1-1, ad6-1 and AdPC-1 that had been cured for 15 days (AdPC-1-1), 16 days (Ad 6-1) or 17 days (Ad 1-1). The results are shown in the following table.

Laminate samples Ad1-1 and Ad6-1 (comprising cured reaction products of adhesives Ad1 and Ad6, respectively) have high strength and product resistance, and are well suited for use as adhesives in laminates for food and other products.

Samples Ad1, ad2, ad4 and Ad6 comprising the high OH functionality polyol product have surprisingly higher room temperature strength, strength at elevated temperatures and product resistance compared to samples Ad3 and Ad5 without the high OH functionality polyol product. When one or more of these properties are desired, it is particularly desirable to use a combination of the transesterified reaction product and the high OH functionality polyol product.

The comparative sample AdPC-1-1 comprising the cured reaction product of the comparative PA-and PC-1 based adhesive has low adhesive strength and very poor product resistance. Neither the comparative sample AdPC-1-1 nor the comparative adhesive AdPC-1 is suitable for use as an adhesive in laminates for food and other products.

Claims

1. An isocyanate-reactive component for reacting with an isocyanate-functional component to form a two-component laminating adhesive comprising a mixture comprising:

a transesterification product comprising a reaction mixture of polymerized polylactic acid and at least one natural oil; and

a high OH functionality polyol product having at least two primary hydroxyl groups and at least two secondary hydroxyl groups,

wherein the amount of transesterification product is from 50 to 85 weight percent based on the total weight of the isocyanate-reactive component.

2. The isocyanate-reactive component of claim 1, wherein the reaction mixture comprises polymerized polylactic acid, at least one natural oil, and a glycol having a molecular weight of 50 to 2000 daltons.

3. The isocyanate-reactive component of claim 1 or 2, wherein the reaction mixture comprises:

polylactic acid, present in an amount of 50 to 85 wt%, based on the total weight of the reaction mixture;

At least one natural oil present in an amount of 13 to 30 weight percent based on the total weight of the reaction mixture;

a glycol present in an amount of 2 to 36 weight percent, based on the total weight of the reaction mixture; and

optionally a transesterification catalyst.

4. The isocyanate-reactive component of claim 1 or 2 having a renewable content in the range of at least 70%.

5. The isocyanate-reactive component of claim 1 or 2 having a viscosity of 3,000 to 20,000cps at 25 ℃.

6. The isocyanate-reactive component of claim 1 or 2, wherein the high OH functionality polyol product is a high OH functionality polyether polyol product.

7. The isocyanate-reactive component of claim 1 or 2, wherein the natural oil is castor oil and/or soybean oil.

8. A two-component adhesive for laminated flexible packaging material comprising a component a and a component B, wherein component a comprises an isocyanate-functional compound having two or more terminal isocyanate groups per molecule and component B is an isocyanate-reactive component comprising a mixture comprising a transesterification product comprising a reaction mixture of polymerized polylactic acid and at least one natural oil and a high OH functionality polyol product having at least two primary and at least two secondary hydroxyl groups, wherein the amount of the transesterification product is from 50 to 85 weight percent based on the total weight of the isocyanate-reactive component.

9. The two-component adhesive of claim 8, wherein the isocyanate-functional compound is prepared using one or more polyisocyanates.

10. The two-part adhesive of claim 8 wherein the isocyanate-functional compound is prepared using diphenylmethane diisocyanate, modified forms of diphenylmethane diisocyanate, and combinations thereof.

11. The two-part adhesive of claim 8 wherein the isocyanate-functional compound comprises a polyurethane prepolymer reaction product of at least one polyol and an excess of polyisocyanate.

12. The cured reaction product of a two-component adhesive according to any one of claims 8-11.

13. The cured reaction product of the two-part adhesive of any one of claims 8-11 having a minimum room temperature adhesive strength of 200 grams/inch.

14. The cured reaction product of the two-part adhesive of any one of claims 8-11 having a minimum room temperature adhesive strength of 400 grams/inch.

15. A soft laminate comprising the two-component adhesive according to any one of claims 8-11 disposed between a first film surface and a second film surface.

16. A soft laminate comprising the cured reaction product of the two-component adhesive of any one of claims 8-11 disposed between a first film surface and a second film surface.

17. A food container comprising a food product disposed between layers of a soft laminate comprising a cured reaction product of the two-component adhesive of any one of claims 8-11 bonding adjacent films.